Rotary mill head



Dec. 26, 1967 T. E. HARRIS ROTARY MILL HEAD Filed Feb. 16, 1966 INVEN'TOR THOMAS E. HARRIS B Y W'o United States Patent 3,360,205 ROTARY MILL HEAD Thomas E. Harris, Valois, Jacques Cartier, Quebec, Canada, assignor to Dominion Engineering Works, Limited, Lachine, Quebec, Canada, a corporation of Canada Filed Feb. 16, 1966, Ser. No. 527,671 2 Claims. (Cl. 241-182) This invention relates to an improved method of manufacturing mill heads for use with rotary grinding mills such as ball, rod or autogenous mills.

In such mills a cylindrical shell is supported for rotation by means of a pair of conically shaped heads located at the ends thereof. Removable lining or wear plates are attached to the inner surface of the heads, by way of bolts extending through the head.

It has been customary to provide the outer surface of the mill head with a generally smooth surface, the head tapering in section from being relatively thick near the centre adjacent the journal, and becoming progressively thinner towards the periphery of the head. The tapered section results in inner and outer head surfaces which are not parallel, thus necessitating a spot facing operation for the bolt receiving holes to ensure satisfactory seating of the securing nuts or capscrews. A washer of rubber or other flexible material is normally fitted beneath each nut to seal the bolt hole and prevent the leakage of liquid from within the mill structure.

A prior method of providing a nut receiving surface parallel to the inner surface of the head, has been by casting raised rings on the outer surface of the head. However, this method has been found to be unsatisfactory because of the discontinuity of the metal surface when such heads are cast, which has been found to lead to undue stress concentrations.

An object of the present invention is to provide a rotary grinding mill head which is adapted to receive a drill or boring tool without requiring a spot facing operation, and which provides a suitable seat for bolts, nuts and sealing washers to retain lining or wear plates.

The present invention provides a radially outwardly tapered rotary grinding mill head having radius blended concentrically disposed annular lands on the outer surface thereof, whereby bolt holes extending through the lands are reinforced by the metal of the lands, without introducing undue stress concentrations.

In addition to the foregoing it has been found that an axi-symmet-ric rotary grinding mill head having radius blended concentrically disposed annular lands on the outer surface thereof according to the present invention may be readily cast, during which process serious interference with metal flow is avoided and hot spots are minimized.

The present invention provides a mill head for use with a cylindrical mill shell as part of a grinding mill, comprising; a casting of substantially conical form with generally radially outwardly convergent inner and outer surfaces defining a variable thickness, a plurality of apertures arranged on substantially concentric pitch circles, extending through the head from the inner to the outer surface substantially normal to the inner surface for lining or wear plate attachment bolts, annular portions of the outer surface adjacent the pitch circles having a radial width in excess of the diameter of the apertures, and extending substantially parallel with corresponding annular portions of the inner surface adjacent the apertures to provide drill receiving and nut seating surfaces normal to the axis of said apertures, whereby the apertures may be satisfactorily drilled to provide seating for nuts and sealing Washers without preliminary spot facing and whereby the strength of the head adjacent the holes is maintained.

The following is a description by way of example of a preferred embodiment of the present invention, reference being made to the accompanying drawings in which:

FIG. 1 is a plan view of a rotary grinding mill head according to the present invention,

FIG. 2 is a sectional view on the line 22 of FIG. 1 and FIG. 3 is a fragmentary sectional View of a prior art method.

Referring to FIGURES 1 and 2 the mill head 10 has a journal portion 11 and a substantially circular conically shaped flange portion 12 in supporting relation therewith. The flange portion 12 has inner and outer surfaces 13 and 14, the inner surface 13 terminating adjacent the outer rim 15 of the flange at a shoulder 16 adapted to receive a cylindrical grinding mill shell (not shown), Holes 18 located around the periphery of the flange permit attachment of the flange to the mill cylinder by fastening means such as bolts or capscrews (not shown).

The inner surface 13 of the mill head 10 is protected from abrasion during operation, by means of linings or wear plates (not shown), which are attached to the inner surface 13 by way of bolts extending through holes or apertures 19 extending normal to the inner surface 13 and arranged on pitch circles substantially concentric with the rotational axis AA of the mill head.

The outer surface 14 of the mill head comprises a series of substantially concentric stepped portions 20, 21, 22, each portion being radius blended to the adjacent surface portion of the mill head.

It will be seen that the plane annular portions 20, 21, 22 thus provided, permit the bolt holes or apertures 19 to be drilled from the outer surface 14 of the mill head to the inner surface 13 and provides a seat for the nut and sealing washer parallel with the inner surface 13, without the necessity of first spot facing the outer surface 14 in the vicinity of the hole, while at the same time a light yet strong reinforced mill head structure is provided which is relatively easy to cast and in which the generation of high stress levels in the region of the holes 19 is avoided.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A mill head for use with a cylindrical mill shell as part of a grinding mill, comprising; a casting having a substantially conical portion with generally radially outwardly convergent inner and outer surfaces defining a variable thickness casting, a plurality of apertures, arranged on substantially concentric pitch circles, extending through the head from said inner to said outer surface substantially normal to said inner surface to receive lining attachment bolt means, and annular portions of said outer surface adjacent said pitch circles having a radial width in excess of the diameter of said apertures extending substantially parallel with corresponding annular zones of said inner surface adjacent said apertures to provide plane surfaces surrounding said apertures extending normal to the axis of said apertures whereby said apertures may be satisfactorily drilled without preliminary spot facing, and said bolt means may be seated thereagainst.

2. A mill head as claimed in claim 1 wherein said annular zones are radius blended with adjacent outer surfaces of said head to reduce stress concentrations in the vicinity of said apertures.

References Cited UNITED STATES PATENTS 1,309,210 7/1919 Marcy 241183 X 1,553,328 9/1925 Roubal 241182 2,156,321 5/1939 Sutherland 241298 X 2,218,580 10/1940 Kennedy 241-182 X WILLIAM W. DYER, JR., Primary Examiner. W. D. BRAY, Assistant Examiner. 

1. A MILL HEAD FOR USE WITH A CYLINDRICAL MILL SHELL AS PART OF A GRINDING MILL, COMPRISING; CASTING HAVING A SUBSTANTIALLY CONICAL PORTION WITH GENERALLY RADIALLY OUTWARDLY CONVERGENT INNER AND OUTER SURFACES DEFINING A VARIABLE THICKNESS CASTING, A PLURALITY OF APERTURES, ARRANGED ON SUBSTANTIALLY CONCENTRIC PITCH CIRCLES, EXTENDING THROUGH THE HEAD FROM SAID INNER TO SAID OUTER SURFACE SUBSTANTIALLY NORMAL TO SAID INNER SURFACE TO RECEIVE LINING ATTACHMENT BOLT MEANS, AND ANNULAR PORTIONS OF SAID OUTER SURFACE ADJACENT SAID PITCH CIRCLES HAVING A RADIAL WIDTH IN EXCESS OF THE DIAMETER OF SAID APERTURES EXTENDING SUBSTANTIALLY PARALLEL WITH CORRESPONDING ANNULAR ZONES OF SAID INNER SURFACE ADJACENT SAID APERTURES TO PROVIDE PLANE SURFACES SURROUNDING SAID APERTURES EXTENDING NORMAL TO THE AXIS OF SAID APERTURES WHEREBY SAID APERTURES MAY BE SATISFACTORILY DRILLED WITHOUT PRELIMINARY SPOT FACING, AND SAID BOLT MEANS MAY BE SEATED THEREAGAINST. 